1. Field of the Invention
This invention relates to turbochargers and, more particularly, to a lubricating mechanism of a turbocharger arranged in association with an automobile vehicle engine.
2. Description of the Prior Art
In FIG. 1 showing a conventional turbocharger arranged in association with an automobile vehicle, the turbocharger 10 includes a turbine housing 13 which has an inlet 11 and an outlet 12 for the engine exhaust combustion gases, a compressor housing 15 which has an air inlet 14 and a compressed air outlet, and an intermediate housing 20 which supports a rotatable shaft 18 by means of a bearing 19 of a floating bushing. The rotatable shaft 18 has positioned on one end thereof a turbine wheel 16 which is positioned within the exhaust passage and has positioned on the other end thereof a compressor wheel 17 which is positioned within the air passage. Rotatable shaft 18 has a small diameter portion to which a collar 22 is secured by means of a screw via the compressor wheel 17.
Since the bearing 19 is limited in the leftward movement as shown in FIG. 1 thereof via the collar 22 by means of a thrust bearing 23 which is arranged for the rotatable shaft 18 and the right end of the bearing 19 faces an enlarged oil distribution portion 24, the bearing 19 also functions as axial direction bearing of rotatable shaft 18. Numeral 21 denotes a seal plate.
In such a conventional turbocharger, however, the gap between the rotatable shaft and the inner surface of the bearing 19 is small and the gap between the right end of the bearing 19 and the left end surface of the oil distribution portion 24 is small. Therefore, the lubricating oil which is supplied from a lubricating oil inlet 25 to a lubricating oil outlet 26 to thereby lubricate between the rotatable shaft 18 and the housing 20 may not be allowed to flow smoothly. As a result, the temperature of the lubricant increases and the viscosity of the lubricant is lowered such that the lubricating characteristic thereof decreases. Accordingly, the rotatable shaft is caused to be worn at a relatively high rate, especially at the side of the turbine wheel 16 which is exposed to the high temperature exhaust gases.